# Comparing and Contrasting AC and DC

#### Belle&Buster4eva

Joined Oct 4, 2008
2
How do you Compare and Contrast AC and DC? So far i've got
'A.C, or Alternate Current, electricity is mainly used for Mains Electricity and is constantly changing directions. The to and fro motion occurs up to 50-60 times per second, depending on the electrical system in the country. An AC generator not only create AC but determines the frequency. The special thing about AC is that the voltage can be readily charged so it is more suitable for long-distance transmission.
In comparison, D.C, or Direct Current, electricity is mainly produced by batteries. The acid inside the batteries create a chemical reaction creating the DC electric charge used to power many things e.g. a torch. Another type of battery that creates DC is a car battery. A car battery has two lead plates inside that are suspended in sulphuric acid. When the plates are given a charge from the car generator a chemical reaction makes them change chemically and they hold the charge. This power then can be used to power the car lights and other things in the car. DC is the continuous flow of negatively charged electrons through a wire. Consisting of a lot of resistance, the electrons flow through like water through a hose. This is because the potential, or pressure, builds up at one end of the wire, due to the excess of the negatively charged electrons. ' Is this enough?
HELP!

#### studiot

Joined Nov 9, 2007
4,998
The special thing about AC is that the voltage can be readily charged so it is more suitable for long-distance transmission.
Yes with the spelling correction - ?changed?

This is very important, why would people wish to change the voltage?

To minimise power losses due to cable resistance. These losses are the same for DC and AC, and increase with increasing current. But power equals voltage times current so to transmit a given amount of power, the higher the voltage the lower the current and the lower the losses.

#### hgmjr

Joined Jan 28, 2005
9,029
In comparison, D.C, or Direct Current, electricity is mainly produced by batteries.
I think your wording in the sentence above may be a bit misleading. While batteries are an important source of DC voltage, to state that they are the main source may be difficult to justify. Batteries share this distinction with DC power supplies both of the linear and switchmode type.

You may want to consider altering the wording to:
In comparison, D.C, or Direct Current, is a source of constant voltage. An increasingly important source of DC electricity is a battery.
hgmjr